My first company sponsored me the green card application after 6 months I
joined their company based on the agreement. My title was staff accountant
and category was EB3 even though I have a masters degree. The category is
determined by job requirements not diploma.
As long as your employer agrees to sponsor this application, they will
handle all the documentation work. No worry about that part since the HR and
your manager/director will get instructions and guidance from the
immigration attorneys coordinated with the company.
My employer posted the job position I was working for in two or three job
market resources. My director told me that HR gave her about 10-12 selected
resumes. She selected three or six (cannot remember clearly) resumes to
clarify the reasons that the candidate did not qualify that position and
then sent the documents to the immigration attorney.And then the employer's
work was pretty much done.
It will definitely take your manager some time and efforts to complete this
process. However, they can always get instructions from the immigration
attorneys. If you really contribute lots of value to your department, your
employer would like to take some time to help you in GC application.
Hope this helps.